The development and validation of a positive and negative outcome expectation scale for re-donation among blood donors

Blood donor retention is an effective way to improve blood safety and maintain a stable blood supply. According to the social cognition theory, outcome expectation is an important determinant of behavioral maintenance. However, no outcome expectation scale for blood donation is available in the literature. The aim of the present study was to develop and validate a positive outcome expectation scale (POES) and a negative outcome expectation scale (NOES) for re-donation among blood donors. In Study 1, a total of 12 items for POES and 7 items for NOES were developed. Exploratory factor analysis (EFA) was performed to examine the factor structure of the two scales among a convenience sample of 155 college student blood donors in China (100 females, 55 males; M-age = 20.23 +/- 1.94). In Study 2, the factor structure was further validated with a second convenience sample of 164 blood donors recruited from blood collection sites (79 female, 85 males; M-age = 25.68 +/- 7.87) using confirmatory factor analysis (CFA). The internal consistency, convergent validity, discrimination validity and criterion validity were also tested. In Study 1, one item from NOES with a communality value lower than .30 was deleted. A three-factor structure for POES and a two-factor structure for NOES were established through the EFA. These factor structures were further supported by the CFA in Study 2. Both POES and NOES showed satisfactory internal consistency, convergent validity, discrimination validity and criterion validity. The POES and NOES demonstrated good reliability and validity in measuring the positive and negative outcome expectations of re-donation among blood donors. The two scales can be utilized in research and practice in predicting and promoting blood re-donation.